In the past, hydraulically needled (i.e., spunlaced) nonwoven fabrics have typically been made from a dry-laid precursor web, either carded or air-formed. These webs are most often hydraulically needled in unbonded form. In particular, spunlaced fabrics are generally made by continuously air-laying a batt of fibrous material and then immediately hydraulically needling the batt using high pressure water jets. A schematic view of such a continuous air-lay process is shown in FIG. 40 of U.S. Pat. No. 3,485,706 (Evans). In addition, such processes are described in White, C. F., "Hydroentanglement Technology Applied to Wet-formed and Other Precursor Webs", Nonwovens, Tappi Journal, pp. 187-192 (June 1990).
More recently, it has also become desirable to hydraulically needle webs that have been formed from wet-laid precursor webs. For example, U.S. Pat. No. 4,891,262 (Nakamae et al.) discloses hydraulically needling wet-laid webs made up of 100% staple length fibers. While these webs have many advantageous properties, the webs lack the abrasion resistance, lint resistance and washability necessary for certain end-uses (e.g., medical apparel and wiper applications).
Another problem associated with conventional wet-laid webs, as well as dry-laid webs, is that they do not have enough integrity to hold together during reeling or shipping operations. As noted by C. F. White, one of the specific problems associated with wet-formed precursor webs is being able to form them, reel them, and transport them to other locations. In continuous air-lay systems this is usually not a problem because the batts are hydraulically needled immediately after they are formed. Thus, as depicted in the Evans patent, web formation and hydraulic needling take place in a continuous series of steps.
It has become increasingly desirable to eliminate the large amount of equipment necessary to form such webs from the front portion of a hydraulic needling operation. Less equipment would be necessary and space would be saved if the wet-laid or dry-laid web could be transported to the hydraulic needling station in the form of pre-made roll goods. Thus, in some operations it is desirable to make web formation and hydraulic needling discontinuous steps which preferably take place at different locations.
Therefore, what is needed is a process that enables spunlaced nonwoven fabrics to be made with all the key properties of a 100% staple fiber nonwoven web, but wherein web formation and hydraulic needling take place in a discontinuous series of operation steps. The process should enhance the strength and integrity of the formed web so that the web can be transported undamaged to a different location for subsequent hydraulic needling treatment. Preferably, the process should improve the durability and abrasion resistance of the resulting spunlaced fabric. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the detailed description of the invention which hereinafter follows.